Hindfoot Arthrodesis: Procedures, Mechanics, and Rehab

Hindfoot arthrodesis is a surgical procedure used to fuse joints in the back portion of the foot, often performed to relieve pain from arthritis, correct deformities, or stabilize severe injuries. By eliminating movement in affected joints, it can improve function and reduce discomfort for individuals with debilitating foot conditions. However, it also alters biomechanics, making proper technique and rehabilitation essential for optimal outcomes.

Anatomy Of The Hindfoot

The hindfoot is a structurally complex region that serves as the foundation for weight-bearing and movement. It consists of two primary bones—the talus and the calcaneus—which articulate to form joints central to stability and mobility. The talus, positioned between the tibia and calcaneus, lacks direct muscular attachments, relying instead on ligaments and articulations for support. This allows for efficient force transmission but also makes it susceptible to injury and degeneration. The calcaneus, the largest tarsal bone, provides a robust base and serves as the attachment site for the Achilles tendon, which generates the powerful plantarflexion necessary for walking and running.

The subtalar joint, formed by the talus and calcaneus, is critical to hindfoot function, facilitating inversion and eversion to help the foot adapt to uneven surfaces. It is stabilized by ligaments such as the interosseous talocalcaneal ligament, which limits excessive motion. Dysfunction or degeneration of this joint, often due to post-traumatic arthritis or chronic instability, can impair gait mechanics and necessitate surgical fusion.

Another key structure is the talonavicular joint, which connects the talus to the navicular bone and plays a significant role in foot mobility. It works with the subtalar joint to facilitate smooth transitions between pronation and supination during walking. Arthritis or deformity in this joint can significantly alter biomechanics, leading to compensatory stress on adjacent structures.

Types Of Arthrodesis Procedures

Hindfoot fusion can be performed using different approaches, depending on the severity of joint degeneration, presence of deformity, and functional demands of the patient. Subtalar arthrodesis, one of the most common procedures, targets the joint between the talus and calcaneus. It is frequently used for post-traumatic arthritis, tarsal coalition, or chronic instability, stabilizing the hindfoot and alleviating pain, though it reduces the foot’s ability to adapt to uneven surfaces.

For more extensive joint pathology, triple arthrodesis may be indicated. This procedure fuses the subtalar, talonavicular, and calcaneocuboid joints, locking the hindfoot into a fixed position while preserving sagittal plane motion at the ankle. It is often used in patients with severe deformities from conditions such as posterior tibial tendon dysfunction, Charcot-Marie-Tooth disease, or rheumatoid arthritis. While it provides pain relief and deformity correction, it also imposes functional limitations, particularly in side-to-side movement. Nonetheless, long-term studies indicate substantial improvements in pain and mobility when patient selection and surgical technique are appropriate.

For isolated talonavicular joint pathology, talonavicular arthrodesis may be the preferred approach. This is particularly beneficial for midfoot collapse in conditions such as adult-acquired flatfoot or inflammatory arthritis. As this joint is central to hindfoot mobility, its fusion has a pronounced effect on gait mechanics. While it significantly reduces pain and improves stability, it requires compensatory adaptations in adjacent joints, which may contribute to degenerative changes over time.

Techniques And Approaches

Surgical techniques for hindfoot arthrodesis must consider anatomical complexity, biomechanical demands, and the underlying pathology. The approach influences healing time, functional outcomes, and long-term stability. Surgeons choose between open and minimally invasive methods based on joint degeneration, prior surgical history, and the need for deformity correction. Open procedures offer extensive visualization for thorough joint preparation and fixation placement, whereas minimally invasive techniques reduce soft tissue disruption and lower the risk of complications such as wound dehiscence or infection.

Joint preparation is critical for successful fusion, as removing cartilage and shaping surfaces impact bone healing. Surgeons use curettage, high-speed burring, or osteotomes to expose subchondral bone, enhancing osseous integration. In cases of severe deformity or bone loss, autologous bone grafts from the iliac crest or allograft materials fill gaps and promote fusion. The choice of graft depends on patient comorbidities and mechanical demands.

Proper hindfoot positioning is essential, as misalignment can lead to compensatory stress on adjacent joints and altered gait mechanics. Surgeons aim for a neutral to slight valgus position to support weight distribution and ensure adequate dorsiflexion for efficient push-off during walking. Fluoroscopic imaging confirms alignment before fixation is applied. In multiple joint fusions, staged correction may be necessary to sequentially address deformities and prevent excessive strain on soft tissues.

Fixation Hardware

Stabilizing fused joints requires fixation hardware to maintain alignment, promote healing, and withstand mechanical stresses. The choice of fixation depends on bone quality, fusion extent, and patient activity level. Surgeons commonly use screws, plates, or intramedullary nails, each offering distinct benefits. Compression screws, often cannulated for precise placement, provide rigid fixation by applying direct compressive forces across the fusion site, enhancing bone-to-bone contact and accelerating integration.

For extensive fusions or cases involving poor bone stock, locking plates offer additional stability by distributing forces over a broader area. These are especially useful in revision surgeries or osteoporotic bone, as they minimize micromotion and reduce hardware failure risk. Intramedullary nails, inserted through the calcaneus and extending into the tibia, provide strong axial stability while limiting soft tissue disruption. This method is particularly beneficial in tibiotalocalcaneal fusion, where maintaining limb alignment is essential for functional recovery.

Foot Mechanics

Hindfoot arthrodesis significantly alters foot biomechanics, influencing gait, weight distribution, and functional mobility. The fused joints no longer contribute to motion, shifting force transmission and increasing reliance on adjacent joints, particularly the midfoot and ankle. Studies indicate that subtalar or triple arthrodesis increases loading on the talonavicular and tibiotalar joints, potentially accelerating degeneration. The loss of inversion and eversion at the subtalar joint reduces the foot’s ability to accommodate uneven terrain, making walking on slopes more challenging.

The redistribution of forces also affects gait efficiency. Normal walking relies on coordinated ankle dorsiflexion, midfoot mobility, and hindfoot adaptability. With restricted hindfoot movement, patients often develop a stiffer gait, characterized by reduced push-off power and shortened stride length. Research shows that hindfoot arthrodesis alters plantar pressure distribution, increasing loading under the lateral forefoot and heel. Over time, these biomechanical adaptations influence muscle activation patterns, requiring targeted rehabilitation strategies to optimize function and minimize complications.

Rehabilitation Focus

Rehabilitation is essential for restoring mobility, strengthening surrounding muscles, and preventing complications from altered foot mechanics. The process progresses through phases, beginning with immobilization and non-weight-bearing to allow bone healing. Patients are typically placed in a cast or boot for six to twelve weeks, depending on fusion extent and healing response. Strict adherence to weight-bearing restrictions is critical to prevent hardware failure or nonunion, which occurs in approximately 10-15% of cases.

As bone consolidation progresses, controlled weight-bearing activities gradually promote joint stability and neuromuscular adaptation. Physical therapy focuses on strengthening the peroneal and tibialis posterior muscles, which play a compensatory role in foot stabilization. Gait training helps patients adjust to mechanical changes imposed by fusion. Custom orthotics or modified footwear may be prescribed to enhance shock absorption and redistribute plantar pressures, reducing the risk of adjacent joint degeneration. Long-term rehabilitation goals include optimizing balance, improving mobility, and enabling patients to resume daily activities with minimal discomfort.